C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

idling issue's

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Old Apr 28, 2009 | 08:42 AM
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Default idling issue's

here's what i've got going on. just inherited my dad's 91. it has 33k on it and for the last 4 or 5 years it's pretty much sat. he had problems with it years back dying when you would push in the clutch. he had all new injectors put in and a complete tune just three years ago. since i've had it the dying thing has happened twice. i can go out and start it and it idles fine. go for a ride and at every stop no problem. stop and shut the car off 5 min or 2 hours doesn't matter. start it back up then it won't idle. no codes i've checked for that and no service engine light. i've read on here many similar threads with alot of recommendations. any advice before i put myself to the mercy of a local shop is great.
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Old Apr 28, 2009 | 09:44 AM
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possible injectors leaking down--hook a pressure gauge to fuel rail...check if the pressure falls quickly after turning off the engine
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Old Apr 28, 2009 | 09:55 AM
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Originally Posted by TWISTERUP
possible injectors leaking down--hook a pressure gauge to fuel rail...check if the pressure falls quickly after turning off the engine
why would it only do it after the engine has been running the shut off
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Old Apr 28, 2009 | 11:58 AM
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that's typically when it's noticed--if they are leaking down it' s not just when hot starting---it's just when the engine is cold ...A) some of the fuel has dryed up over a longer period of time and.... B) the engine isn't bothered as much by the extra fuel on a cold start...leaking injector cold start complaints are typically a longer cranking time.

It very well may not be the injectors...you'll have posts voting for the IAC valve (and it could be bad) I'm very simply saying..."that's what I'd check first"

Further let me ask this... what does it take to get it to idle when the problem occurs--does it idle at all and just very low rpms---or multiple starting attempts and then keeps running or do you give it throttle and then it starts and runs ??

Last edited by TWISTERUP; Apr 28, 2009 at 12:06 PM. Reason: more info
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Old Apr 28, 2009 | 12:32 PM
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Originally Posted by vabatwho714
here's what i've got going on. just inherited my dad's 91. it has 33k on it and for the last 4 or 5 years it's pretty much sat. he had problems with it years back dying when you would push in the clutch. he had all new injectors put in and a complete tune just three years ago. since i've had it the dying thing has happened twice. i can go out and start it and it idles fine. go for a ride and at every stop no problem. stop and shut the car off 5 min or 2 hours doesn't matter. start it back up then it won't idle. no codes i've checked for that and no service engine light. i've read on here many similar threads with alot of recommendations. any advice before i put myself to the mercy of a local shop is great.
even though the injectors were replaced, they were probably replaced with the OE injector.. That injector was probably an NOS part, They will fail the same as a original multec. So, ohm test the injectors and report the findings. It will take you 20 minutes and if you do it yourself won't cost a penny. If the injectors have bad coils which is very possible it would cause your problem.
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Old Apr 28, 2009 | 12:51 PM
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Originally Posted by FICINJECTORS
even though the injectors were replaced, they were probably replaced with the OE injector.. That injector was probably an NOS part, They will fail the same as a original multec. So, ohm test the injectors and report the findings. It will take you 20 minutes and if you do it yourself won't cost a penny. If the injectors have bad coils which is very possible it would cause your problem.
Hey buddy, how's it going over there in Jawja ? I'm still happy with those Bosch III's you sold me. Picked up a block from a 96 vette and am planning another motor. What size injectors you reckon I ought use in a 350 motor designed to spin 7000 rpm ?
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Old Apr 28, 2009 | 01:00 PM
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Originally Posted by TWISTERUP
that's typically when it's noticed--if they are leaking down it' s not just when hot starting---it's just when the engine is cold ...A) some of the fuel has dryed up over a longer period of time and.... B) the engine isn't bothered as much by the extra fuel on a cold start...leaking injector cold start complaints are typically a longer cranking time.

It very well may not be the injectors...you'll have posts voting for the IAC valve (and it could be bad) I'm very simply saying..."that's what I'd check first"

Further let me ask this... what does it take to get it to idle when the problem occurs--does it idle at all and just very low rpms---or multiple starting attempts and then keeps running or do you give it throttle and then it starts and runs ??
when you push in the clutch the idle drops to around 2 to 300 rpm. you can see the motor is trying to recover. but then it dies. hit the key it fires right up, but you have to massage the gas pedal to keep it running. was talking to a friend that was a mech. at a gm dealer ship. he mentioned checking the IAC. just got the gm factory service manual. went out and got a new fuel filter at lunch too. also i read a thread on here saying not to use " sea foam ". i've got a feeling my dad used it from winterizing. i know he used it with his boats. i will check the injectors tonight. feel alot better having a manual. will post my findings
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Old Apr 28, 2009 | 01:40 PM
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Originally Posted by chriswhewell
hey buddy, how's it going over there in jawja ? I'm still happy with those bosch iii's you sold me. Picked up a block from a 96 vette and am planning another motor. What size injectors you reckon i ought use in a 350 motor designed to spin 7000 rpm ?
hey chris
at least 32, call me i will hook you up and take the bosch 3's in trade.
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Old May 2, 2009 | 06:59 AM
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checked all inj, they all read 16.4 ohms
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Old May 2, 2009 | 08:29 AM
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Originally Posted by vabatwho714
checked all inj, they all read 16.4 ohms

Did you check them with motor both hot & cold? There can be a difference caused by operating temp in there resistance.
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Old May 2, 2009 | 06:10 PM
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Originally Posted by floridamale
Did you check them with motor both hot & cold? There can be a difference caused by operating temp in there resistance.
i checked them with the engine cold
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Old May 2, 2009 | 06:45 PM
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There can be different reading with a hot engine, to be sure the injectors are good I would retest hot. You might want to send a PM to Jon @ FIC also
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